Manufacture of electric cables.



W. F. SMITH.

MANUFACTURE OF ELECTRIC CABLES.

APPLICATION FILED MAY 23. 1914.

1,223,434. Patented Apr. 24, 1917.

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UNITED STATES PATENT OFFICE.

WILLIAM FRANCIS SMITH, OF BROOKLYN, NEW YORK, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF I NEWYORK.

MANUFACTURE OF ELECTRIC CABLES.

Application filed May 23, 1914.

To all whom it may concern:

Be it known that I, WILLIAM FnANois SMITH, a citizen of the UnitedStates, residing at Brooklyn, in the county of Kings and State of NewYork, have invented a certain new and useful Improvement in theManufacture of Electric Cables, of which the following is a full, clear,concise, and exact description.

This invention relates to the manufacture of electric cables, and moreparticularly to the manufacture of pairs of insulated conductors for usein electric cables.

The object of this invention is the production of an eficient electriccable of improved and uniform electrical characteristics.

The process embodying this invention is an improvement over a processdescribed in Patent No. 1,12%,249, issued to Gustavus A. Anderegg,'onJanuary 12, 1915. Recent investigations have shown that in additionto the troubles mentioned in the Anderegg patent, there are numerousothers which also have a deleterious effect upon the uniformity anddegree of the electrical characteristics of electric cables.

It is a fact thatin the coils of wire of commercial form thereappearvarious irregularities in the hardness of the wire.

I These irregularities of hardness have been found to be deleterious inthe finished electric cable as evidenced by the variations in theseparation of the two wires which form a twisted pair, by the differencein length of the two wires forming a pair, and by variations in thehelices in the conductors of the pair.

In accordance with the processes of forming twisted pairs of insulatedconductors heretofore used there have resulted twisted pairs in whichirregular helices appeared in the conductors of any pair and in whichthere were differences in the lengths of the two conductors of any pair.When such pairs have been used in electric cables, the above mentionedirregular helices and the difl'erent lengths of the conductors have hada marked deleterious effect upon the electrical characteristics of thecables.

In order to overcome the deleterious effects just mentioned, thisinvention provides for the forming of the insulated conductors intohelices of the same pitch, and

Specification of Letters Patent.

Patented Apr. 24, 1917.

Serial No. 840,582.

for the equalizing of the length of the two conductors forming a pair.

This invention will be more fully understood by referring to thedrawings show ing one embodiment thereof and wherein,-

Figure 1 illustrates apparatus for straightening and for insulating aconductor;

Fig. 2 illustrates apparatus for equalizing the length of twoconductors, for forming the insulated conductors into helices of thesame pitch and for twisting the conductors together; and

Fig. 3 is a view of part of the apparatus for equalizing the length ofthe conductors.

As shown in the drawings, the apparatus for straightening the conductorsmay conveniently be a wire straightener 4, which consists of two sets ofrollers 5 and 6 rotatably mounted on a frame 7. The apparatus forapplying uniform insulation to the straightened conductor may be aninsulating head 10. This insulating head consists of a plate 11 and ahollow spindle 12 mounted thereon. As the conductor passes through thespindle 12, the insulating head is rotated by any suitable means, as abelt and pulley shown at 13, and insulating tape l-t from a pad of tape15 is guided on to the conductor by means of a guide 16 mounted on theplate 11, a guide 17 supported on the spindle l2, and the upper portionof the spindle 12. The insulating tape 14 is formed 011 the conductor inspiral convolutions. A uniform diameter over the insulated conductor ismaintained and a definite amount of insulation per unit length ofconductor is applied by maintaining a definite relation between thespeed of the conductor and the speed of rotation of the insulating head,combined with the use of an insulating head which definitely centers theconductor within the insulating tape, such an insulating head beingshown in my copending application, Serial No. 793,129 filed October 3,1913. The insulating head described in application Ser. No. 7 93,129consists of a plate having a hollow spindle and guides for theinsulating tape mounted thereon.

Suitable mechanism for twisting the insulated conductors together mayconsist of a revolving shaft 20 carrying a bar 21. Yokes 22, in whichspools 23 containing insulated conductors are supported, are mounted onthe ends of the bar 21. The twisting mechanism may be rotated by meansof a pulley 24 and a belt 25.

Apparatus for equalizing the length of the insulated conductors mayconsist of'a frame 30 mounted ontop of the shaft 20 and yokes 22. In theframe are mounted a plurality of rollers 31, over which are passedendless belts 32, which, at pointsupon opposite sides of the frame 30,are forced together by means of spring pressed shoes 33 slidably mountedonthe frame 30. As the conductors are passed through the equalizingapparatus, each is gripped by the 'two endless belts 32, 32 due to theaction of the spring pressed shoes 33, 33. The gripping of theconductors by the belts causes the travel thereof to be equal to that ofthe conductors, assuming the tension on the shoes to be adjustedproperly. If, therefore, one conductor passes between the belts at acertain rate of speed, the belts will travel at the same rate and sincethe other conductor is gripped by the same belts, it must necessarilytravel at the same rate of speed as the belts and the first mentionedconductor. Consequently, since the speed of the two conductors isequalized, the length of the conductors forming a pair must necessarilybe equal.

The means for forming the insulated conductorsrinto helices of the samepitch may be a rod 40 provided with a plurality of grooves 41 andsupported in the top of the frame 30. A detailed description of theapparatus for equalizing the length of the conductors, and of the meansfor forming the insulated conductors into helices of the same pitch isto be found in Patent No. 1,104,078 issued to me on July 21, 1914.

The wire 42, which is to form the conductor, is passed from a coil 43,through the device 4 which straightens the conductor. The conductor isthen passed through the insulating head 10, which applies thereto adefitered within the insulation.

nite amount of insulation per unit length of conductor. Consequentlythere results an insulated conductor having uniform diameter and inwhich the conductor-is definitely'cen- The insulated conductor is woundonto reels 23, which are placed in the yokes 22 of the twistingmechanism. The insulated conductor from each reel 23 is fed up betweenthe endless belts 32 and into the grooves of the rod 40. As the twistingmechanism is rotated, the insulated conductors are drawn forward andengaged by the endless belts 32, which equalize the speed thereof,thereby equalizing the "length of the conductors. The insulatedconductors, in passing through the grooves 41, of the rod 40. are formedinto helices of the same pitch. The rotation of the whole mechanismcauses the conductors to be twisted together.

What is claimed is:

l. The method of forming a twisted pair of insulated conductors whichconsists in covering each conductor with insulation, separately formingthe insulated conductors into helices of the same pitch, and thenbringing the helically formed insulated conduotors together to make atwisted pair.

2. The method of forming a twisted pair of insulated conductors whichconsists in covering each conductor with insulation, feeding theinsulated conductors forward at the same speed, separately forming theinsulated conductors into helices of the same pitch, and then bringingthe helically formed insulated conductors together to make a twistedpair.

In witness whereof, I hereunto subscribe my name this 20th day of May,A. D. 1914.

WILLIAM FRANCIS SMITH.

Witnesses:

RAY G. Horooon, E. EDLER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. G.

